Phytases (myo-inositol hexakisphosphate phosphohydrolase: EC 3.1.3.8) are enzymes that hydrolyze phytate (myo-inositol hexakisphosphate) to myo-inositol and inorganic phosphate. The enzymes are known to be valuable feed additives. At the close of the twentieth century, annual sales of phytase as an animal feed additive were estimated to exceed $150 million and were growing.
Poultry and pig diets are currently based primarily on cereals, legumes, and oilseed products. About two-thirds of phosphorus (P) present in these feedstuffs occurs as phytates, the salts of phytic acid. Phytate phosphorus in plants is a mixed calcium-magnesium-potassium salt of phytic acid that is present as chelate and its solubility is very low. Phosphorus in this form is poorly digestible for monogastric animals such as human, swine, and poultry.
For the utilization of phytate phosphorus and minerals and trace elements bound in phytic acid complexes, hydrolysis of the ester-type bonded phosphate groups of phytic acid by phytase is necessary. Phytases belong to a special group of phosphatases which are capable of hydrolyzing phytate to a series of lower phosphate esters of myo-inositol and phosphate. Two types of phytases are known: 3-phytase and 6-phytase, indicating the initial attack of the susceptible phosphate ester bond. Although monogastric animals lack sufficient phytase to effectively utilize phytate phosphorous, many fungi, bacteria and yeasts produce phytase that can be used to supplement animal rations.
The beneficial effects of supplementary phytases on phosphorus digestibility and animal performance have been well documented (Mroz et al., 1994; Kornegay et al., 1996; Rao et al., 1999; Ravindran et al., 1999). The efficacy of enzyme preparation depends not only on the type, inclusion rate and level of activity present, but also on the ability of the enzyme to maintain its activity in the different conditions encountered through the gastrointestinal tract and the conditions used for the pre-treatment of a food or feed formulation.
Although numerous phytases are available for use as a supplement, many of the enzymes have certain disadvantages. For example, many of the currently used phytases lose activity during feed pelleting processes due to heat treatment. Additionally, many of the currently used phytases are not adequate in instability for proteases in animal digestion systems such as pepsins and chymotrypsins.
There is a need for a phytase with improve properties for use in animal feed and food processing.